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38 Cards in this Set
- Front
- Back
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Anatomy of an Earthquake
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Stress on rocks is energy
Elastic deformation – energy released as earthquake Plastic deformation – energy used to deform rock |
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Earthquake
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– sudden motion or trembling caused by the abrupt release of energy that is stored in rocks.
Slippage: minor movement Fracture: larger movement |
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Earthquake waves
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Waves – transmit energy
Seismic waves – waves that travel through rock Seismology – study of earthquakes and Earth’s interior using seismic waves |
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Focus
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– rupture point where energy is released
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Epicenter
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– point on Earth’s surface directly above the focus
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Body Waves
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waves that travel through the Earth’s interior
P wave – compressional elastic wave S wave – shear wave |
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Surface waves
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slower waves
Rolling (up/down) waves Side-to-side vibrations |
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Measuring seismic waves
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Seismograph – the instrument
Seismogram – the record it makes |
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Measuring Earthquakes
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Mercalli scale – measures damage
Richter scale – measures energy Moment-magnitude – measures energy as a function of movement and fault surface area |
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locating earthquakes
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P-S waves travel at different speeds
This allows us to calculate distance Time-travel curve Distances from multiple observations finds a location |
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Transforming Boundaries: San Andreas
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Strike-slip fault
Fault is vertical Movement is along the line of the fault Fault creep – small, slow movements along fault |
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Convergent Boundaries
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one plate sliding under another
Benioff zone – friction along the down-plunging contact zone Pacific NW evidence India-Pakistan border, 2005 |
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Divergent boundaries
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– spreading centers
Friction along sliding blocks Mainly shallow |
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In plate interiors
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– infrequent
1811-12, New Madrid, MO Area is still seeing deformation |
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Earth Quake Prediction
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Long-term prediction
Tells where EQs are likely to occur Short-term prediction Can indicate place and time Foreshocks Monitoring China, Japan |
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Cost-benefit analysis (CBA)
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Define the risk
Note the frequency Calculate the cost |
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Tsunami
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– seismic sea wave
Undersea fault motion Far-traveling wave Coastal hazard |
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Studying the earth's interior: Wave Behavior
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In homogenous media, waves propagate equally in all directions
Velocity ~ nature of medium When moving from one medium to another, waves bend (refraction) |
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Studying the Earth’s Interior
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Andrija Mohorovičić (1909)
Refraction – waves arrived at distant earthquakes faster than closer ones Boundary is named the Mohorovičić discontinuity (or Moho) |
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Structure of Mantle
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2900km thick
At 660km down – a discontinuity (refraction again) |
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Discovery of Core
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Refraction indicates liquid
Refraction creates a shadow zone of seismic waves |
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Density of Earth
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Density of Earth
Average of 5.5 g/cm3 Crust – 2.5 to 3.0 g/cm3 Mantle – 3.3 to 5.5 g/cm3 Core – 10-13 g/cm3 |
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The Earth;s magnetism
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Probably electromagnetic in nature
Too hot for permanent magnetization Likely occurs in outer core Magnetic fields occur on several planets |
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1. A rock that has deformed __________ under stress keeps its new shape when the stress is released.
a. elastically b. non-permanently c. plastically d. flexibly |
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2. __________ is the study of earthquakes and the nature of Earth’s interior based on elastic waves traveling through rock, produced by an earthquake.
a. Seismology b. Cosmology c. Seismicity d. Ecology |
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3. The initial rupture point of an earthquake (below Earth’s surface) is the __________.
a. focus b. disaster zone c. releaser d. epicenter |
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4. __________ waves are elastic waves traveling through rock, produced by an earthquake.
a. Tidal b. Seismic c. Electromagnetic d. Ocean |
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5. The __________ is located on Earth’s surface directly above the initial rupture point of an earthquake.
a. fault b. upper center c. focus d. epicenter |
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6. __________ waves are the fastest body waves generated by an earthquake.
a. P b. Q c. R d. S |
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7. A seismograph measures __________.
a. Earth’s temperature b. magnetic anomalies c. ground vibrations d. isostasy |
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8. The __________ scale measures the total amount of energy released during an earthquake, based on the amount of movement and the fault surface area.
a. Mercalli b. Roncalli c. Richter d. moment magnitude |
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9. To measure the distance from a recording station to an earthquake epicenter, geologists evaluate the __________ with a time-travel curve.
a. magnitude of an earthquake b. refraction of P and S waves c. amplitude of the largest earthquake waves d. interval between the arrival of P and S waves |
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10. A strike-slip fault is a __________ fault on which rocks on opposite sides move __________.
a. vertical, horizontally b. vertical, vertically c. horizontal, vertically d. horizontal, horizontally |
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11. __________ is a continuous, slow movement of solid rock along a fault, usually not causing large earthquakes.
a. Fracturing b. Fault slipping c. Fault creep d. Strike-slip |
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12. A Benioff zone is an earthquake zone at a __________ plate boundary
a. transform b. subduction (convergent) c. divergent d. rifting |
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13. During the process of __________, soil loses its shear strength and becomes a fluid.
a. liquefaction b. liquidation c. subduction d. fault creeping |
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14. The Mohorovicic discontinuity is the boundary between __________ and __________.
a. crust, mantle b. mantle, outer core c. outer core, inner core d. continental crust, oceanic crust |
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15. Geologists learned that the outer core is liquid because __________ do not travel through the outer core.
a. surface waves b. tsunamis c. P waves d. S waves |
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